Balanced impeller for centrifugal pumps



June 9, 1953 1-. w. JOHNSON BALANCED IMPELLER FOR CENTRIFUGAL PUMPSFiled NOV. 22, 1949 2 Sheets-Sheet 1 INVENTOR.

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June 9, 1953 Filed NOV. 22', 1949 T. W. JOHNSON BALANCED IMPELLER FORCENTRIFUGAL PUMPS FIG. 3

2 Sheets-Sheet 2 v IN VEN TOR.

T HOMAS W OHNSON BY Patented June 9, 1953 BALANCED IMPELLER FORc'ENTRIFUGAL PUMPS Thomas W. Johnson, Parsippany, N. J., assignor toBendix Aviation Corporation, Teterboro, N. J a corporation of DelawareApplication November 22, 1949, Serial-No. 128,813

The present invention relates to centrifugal pumps and particularly tomeans and methods for balancing the axial reactive forces on theimpellers thereof.

r The action of the impeller during the opera- 5 of theinvention. tionof the pump is to hurl the fluid into the de- Referring to the drawinwherein like referlivery chamber from the impeller chamber thereeneecharacters designate l p r by causing a pressure gradient to exist aboutFig. 1 iS an ele p y in section of a the impeller. The effect of thispumping action Centrifugal P p assemblyis to cause more fluid to flowinto the pump cas- 8 2 is a perspective view of the impeller, rear ing,and as the action of the impeller is conce upw rdstinuous, the pressuregradient above-mentioned 3 is a View Showing the'lelative magnituderemains continuously across the impeller. Be- 0f the unbalanced areas ofe peller. cause of the difference in area of the face of the Referring HW t th draw s d more p rear shroud and the face of the front shroud ofula y to F a Ce t fugal pump generally the impeller, the impeller andshaft are subdesig by he numeral 10 comprises a casjected to anundesirable axial thrust, illg l2 and inlet l4 and outlet is. The casingIt is, therefore, one of the objects of the presit contains an impellerchamber 18, having front ent invention to provide a novel method ofbaland rear walls It and 2|, respectively, and where-' ancing theimpeller means whereby the foregoing in the impeller 29 is free torotate, driven y the disadvantage is eliminated, and to do so in a a t22 which is coupled to the source of ronovel and effective manner. tarypower 24. Casing l2 also contains an outlet Another object of theinvention is to provide chamber l8a peripherally disposed about impelleran impeller for a centrifugal pump whereby sevof chamber I8 andcommunicating therewith. The eral of the power losses now present areelimseal 26 of the shaft 22 is considerably smaller in mated, diameterthan inlet conduit 28, which difference Another object of the inventionis to provide contributes-to the unbalance of the axial loads on animpeller for a centrifugal pump whereby the impeller as hereinafterexplained. A seal shallow grooves of a specified size and numberencompasses e aft 2 and prevents leakage on the rear of the shroud actas non-deliver- 3 from the chamber l8. The impeller 20 includes ingcentrifugal pumps so as to create a pressure a front shroud 32 and arear shroud 34 held on the shroud to balance the other fluid forcestogether by pins 35. Vanes 31 are provided thereon. in the'rear shroud34 and open from the interior Still another object of the invention isto proof the impeller 20 to the chamber 18 and outlet vide a balancedimpeller for a centrifugal pump 35 chamber 18a. 7 I thereby obviatingthe necessity for thrust bear- During normal operation of the pump, aclearings on the impeller. ance space A between the front shroud 32 ofthe Another object of the invention is to balance impeller and the frontwall IQ of impeller chamth fgrces on t impeller of a t if l pump ber l8,and a clearance space B between the rear in such a manner to permit ashorter overall 40 Shroud 34 0f e i p and the rear Wall 2| pump lengthof chamber l8 are filled with fluid from the Still another object of theinvention is to inoutlet chamber |8a and therefore, the shrouds creasethe efficiency of a centrifugal pump by 32 and 34 are subjected topressure therefrom eliminating the energy losses caused by the longioverthe surfaces 36 and 38, respectively (Fig. 3). tudinal pull on theimpeller. Referring now to Fig. 2, the rear shroud 34 of Still anotherobject of the invention is to prothe impeller 20 contains a series ofrelatively vide means of the above-indicated character shallow slots 40radially disposed about the which shall be simple and economical tomanperiphery thereof and extending towards the ufacture and install, yetpositive and reliable in shaft 22. The length L of the slots 40 isadjusted operation. as hereinafter explained depending upon the Theforegoing and other objects and adrelative unbalance of the impeller.vantages will appear more fully hereinafter from Having thus explainedthe invention, it will a consideration of the detailed description whichnow be apparent to those skilled in the art that follows, taken togetherwith the accompanying when a fluid from the inlet I4 is drawn into thedrawings, wherein one embodiment of the invenimpeller 20 and hurledagainst the walls of the 2 Claims. (01. 103-103) tion is illustrated byway of example. It is to be expressly understood, however, that thedrawings are for the purpose of illustration only, and are not to beconstrued as defining the limits outlet chamber [8a for ejection throughthe outlet It, all of the clearance space between the front shroud 32and on the surface 38 of rear shroud 34. the rear shroud 34 and rearwall 2! of chamber [8 will become filled with fluid which will exercisea pressure on the surface 36 of the front shroud 32 and on the surface32 of rear shroud 34.

Since the surface 38 is greater than the surface 36, partly because ofthe greater diameter of the inlet conduit 28 compared to the seal 24 ofthe shaft 22, the pressure on the rear Shroud 34 would ordinarily begreater than the pres. sure on the front shroud 32 thereby causing anundesirable axial component in the direction of the inlet I4. However,the slots 40 in the rear shroud 34 impart a turning swirling action tothe fluid between the face 01 the rear shroud, 34 and the adjacent rearwall IQ of chamber I8, and in effect act as non-delivering centrifugalpumps, with the result that the total pressure on the rear shroud 34 isreduced tending to balance ra her than over ome the pr ssure on thefront shroud, 32.

It is to be noted that the invention permits extremely finite balancingof the impeller forces since the shallow grooves 40 may first be cut ofinsufficient length L to balance the impeller, and the operation testedand then gradually increased in length L after each test run, there.bygradually approaching and ultimately reaching the precise balancepoint.

There are thus provided means for balancing the forces on the impellerof a centrifugal pump which are simple and economical to manufacture andyet positive and reliable in operation and which obviate the necessityfor expensive thrust bearings.

It is further to be noted that the invention accomplishes the balancingof the impeller without the necessity of increasing the overall pumplength since the fluid swirling means are contained within the impelleritself without protruding therefrom.

Although only one embodiment and one ap-s plication of the invention hasbeen illustrated and described, other changes in form and relativearrangements of the parts may be made to suit requirements.

What is claimed is:

1. In a centrifugal pump of the type including a casing, an impellerchamber in said casing having front and rear walls, an axial inlet saidfront wall, an outlet including an outlet chamber peripherally disposedabout said im-, peller chamber, and an impeller mounted for rotation insaid impeller chamber, said impeller having front and rear shroudsarranged in spaced relationship with the front and rear walls of saidimpeller chamber and pumping vanes interposed between said front andrear shrouds, said inlet opening into the interior of said im-. pellerwhereby the rotation of said impeller pumps a fluid from said inlet tosaid outlet, and said impeller being effected by an unbalanced pressuredistribution over the inner and outer surfaces of the front and rearshrouds upon Cal the pumping of a fluid as aforesaid, the improvementcomprising a plurality of shallow grooves formed in the outer radialsurface of said rear shroud opposite said inlet, said grooves extendingradially inwards from the periphery of said rear shroud and effectiveupon the retation of said impeller to rotate the fluid between said rearshroud and the wall of said impeller chamber adjacent said rear shroudwhereby the rotational velocity of the rotating fluid is greatestadjacent the periphery of said rear shroud and the forces produced onthe surface of said rear shroud by said rotating fluid are effective tobalance the summation of all forces acting on the remaining surfaces ofsaid impeller.

2', In a centrifugal pump of the type including a casing, an impellerchamber in said casing having front and rear walls, an axial inlet insaid front wall, an outlet including an outlet chamber peripherallydisposed about said impeller chamber, and an impeller mountedforrotation in said impeller chamber, said impeller having front andrear shrouds arranged in spaced relationship with the front and rearwalls of said impeller chamber and pumping vanes interposed between saidfront and rear shrouds, said inlet opening into the interior of saidimpeller whereby the rotation of said impeller pumps a fluid from saidinlet to said outlet, said rear shroud having a greater outer surfacethan the outer surface of said front shroud whereby a greater force isproduced on said rear shroud upon rotation of said impeller to pump afluid from said inlet to said outlet;- the improvement comprising aplurality of radial grooves formed in the outer surface of said rearshroud, said radial grooves extending inwardly from the periphery ofsaid rear shroud and terminating short of the center thereof, saidradial grooves being effective upon the rotation of said impeller toproduce a whirling of the fluid between said rear shroud and said rearwall to thereby produce a pressure distribution on the outer SUI. faceof said rear shroud decreasing proportionately from a high valueadjacent the periphery of said radial grooves toward a lower valueadjacent the inner ends thereof whereby the forces on the front and rearshrouds are equalized.

THOMAS W. JOHNSON.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 633,732 Price Sept. 26, 1899 2,228,207 Forssell Jan. 7, 19412,247,813 Huitson July 1, 1941 2,361,521 Yates Oct. 31, 1944 FOREIGNPATENTS Number Country Date 443,332 Germany Apr. 26, 1927 698,291 Frances Nov. 17, 1930

